Photoelectric device for the determination of the position of line markings

ABSTRACT

A photo-electric device for the determination of the position of line markings with a swinging element in a way path, through which a light stream impinging upon a photo-electronic element is periodically varied, which comprises a swinging element and a switch controlled by the movement of the swinging element. A photo-electronic element emits and electric output signal. Two channels are provided and the switch connects alternately the electric output signal with one of the channels. The switching takes place at about the turning point of the swinging element, so that the reciprocation of the swinging element causes a series of impulses in the two separate channels. Means are provided for the determination of the relative phase position of two harmonic oscillations of equal frequency, contained in each of said series of said impulses.

O United States Patent [151 3,681,605 Schmitt [451 Aug. 1, 1972PHOTOELECTRIC DEVICE FOR THE DETERMINATION OF THE POSITION PrimaryExaminer-James W. Lawrence OF LINE MARKINGS Assistant Examiner--T. N.Grigsby [72] Inventor: Waiter Schmitt, Egerer, Germany Atmmey EmestMcmtague [73] Assignee: Fit-ma Dr. Johannes Heidenhain, [57] ABSTRACTTraunreut Traunstem Germany A photo-electric device for thedetermination of the [22] Filed: Aug. 4, 1970 position of line markingswith a swinging element in a way path, through which a light streamimpinging [21 1 Appl' 60842 upon a photo-electronic element isperiodically varied,

which comprises a swinging element and a switch con- [30] ForeignApplication Priority Data trolled by the movement of the swingingelement. A photo-electronic element emits and electric output 1969Germany 19 39 signal. Two channels are provided and the switch connectsalternately the electric output signal with one of the channels. Theswitching takes place at about the [58] meld f' 250/206 356/167 turningpomt of the swinging element, so that the reciprocation of the swingingelement causes a series of impulses in the two separate channels. Meansare [56] References Cited provided for the determination of the relativephase UNITED STATES PATENTS position of two harmonic oscillations ofequal frequen- 3 454 776 l 969 Hock 250/232 cy, contained in each ofsaid series of said impulses. 3:502:415 3/1970 Hock ..250/232 X 4Claims, 1 Drawing Figure 1 3 l' l l a a TEEE f mass AFTER I mumoz.CIRCUIT PHOTOELECTRIC DEVICE FOR THE DETERMINATION OF THE POSITION FLINE MARKINGS The present invention relates to a photo electric devicefor the determination of the position of line markings with a swingingelement in the path of the rays, through which the light beam impingingupon a photo-electric member varies periodically. The swinging elementcan be, for instance, a swinging mirror, a swinging plate with parallelfaces, a swinging screen or a swinging wire. The swinging element isexcited by an electric alternating voltage in any known manner for aswinging operation. In case of a tensioned wire, as a swinging element,this can be performed in known manner such, that the wire is tensionedin a magnetic field and is passed by the exciting alternating current.

The image of the line marking is disposed in the swinging plane of thetensioned wire. in case of swing ing mirrors or plates with parallelfaces, a particular screen is required in the ray-path, on which theline marking is imaged. In each case the movement of the swingingelement causes at the same moment a variation of the light current, bymoving the image of the line marking over the screen or the screen overthe image of the line marking. Since the swinging element performs aperiodic movement, also a periodic light current variation will takeplace, which expresses itself again in a periodic variation of thesignal emitted from the photo-electronic member. Generally, thus, aseries of electrical impulses is created.

The determination of the position of the line marking relative to thescanning device takes place in known devices of this type either such,that a comparison of the times takes place, which are disposed betweenthe brushing-over of the line marking by the screen in the forward-andreturn-run and, on the other hand, between the brushing-over in thereturn-and forwardrun. A device has become known also, however, in whichthe series of impulses emitted from the photoelectronic element anunstraight harmonic is sieved out and in which the phase position ofthis harmonic is compared with the phase position of the correspondingharmonic, which is derived from the excitementfrequency for the swingingelement.

The known devices of the first mentioned type have the drawback, but, incase of non-symmetrically formed line markings, measuring errors arecreated. Furthermore, a further measuring non-safety is created such,that only a few discrete time points of the total signal period didcontribute to the measuring, because the signal is triggered in theseknown devices at a predetermined signal height. Due to the noise of thesignal, a certain un-safety results for the time point of triggering.The second mentioned known device has the drawback, that it is suitableonly as a zero-instrument and has only at all in the neighborhood of thezero-evener a sufiicient sensitivity. By this arrangement thus onlysettings can be obtained, in which the position of the line marking doesnot deviate from the zero position. For other positions of the linemarking, a particular measuring system must be provided, which displacesthe line marking or its image so far, that the photo-electric scanningdevice can operate as a zeroinstrument. lnstead the displacement of theline marking, in the last mentioned device, as a matter of course, alsothe scanning screeen can be displaced measurably.

This brings about, however, the same drawbacks, namely the requirementof a very exact measuring device.

On the other hand, it can appear desirable, that the photo electricscanning device permits, with the same exactness and sensitivity, withwhich a setting to zero can take place, to measure also variations andto set the same, without requiring therefor an additional measuringsystem.

It is one object of the present invention to provide a photo-electricdevice for the determination of the position of line markings, whereinthe drawbacks of the known devices are avoided and to create aphoto-electric device of the type set forth above, which cannot onlyoperate exactly extensively independent from the formation of the linemarkings, which, however, is also suitable as measuring system forlinear displacements of the line markings within a predetermined range.

It is another object of the present invention, to provide aphoto-electric device for the detennination of the position of linemarkings, wherein the object is obtained in the first place by a switchcontrolled by the movement of the swinging element, which switchconnects the electrical output signal delivered from thephoto-electronic member, alternately with one of two channels, wherebythe switching takes place about in the reversal time point of theswinging element, so that the forward-and return-run of the swingingelement cause an impulse series each in the two separate channels, andwhich is furthermore characterized by means for the determination of therelative phase position of two harmonic oscillations of the samefrequency, which are contained each in one of the two impulse series.The switching over must not effect necessarily the electronic outputsignal of the photo-electronic member, rather it can already take placeprior to the transformation of the light current into an electric signalpurely optically, by example, by optical polarization.

The mentioned device permits also, by selection of a harmoniccorresponding to the high order number to increase selectively thesensitivity and exactness, however, by taking in stride of a certainmulti-interpretation within the path covered by the swinging element. Inaccordance with the present invention, however, also a high exactness aswell as a single meaning of the indication can be obtained such, thatthe arrangement in accordance with the present invention is applied fora higher harmonic, as well as for a lower harmonic simultaneously. Thehigher harmonic delivers thereby the high exactness, and the lowerharmonic secures the single meaning of the indication.

Suitably, means are provided for the production of a harmonicoscillation from the excitement-frequency of the swinging element andphase displacement for these harmonic oscillations, which automaticallybring about the harmonic swinging derived from the exciting frequencyinto a rigid phase relation to the harmonic oscillations of equalfrequency, contained in both impulse series. Contrary to the knowndevice, in which likewise harmonic upper waves are used for themeasuring, in the case of the present invention, however, the comparisonof a harmonic from the photo-electric signal with the correspondingharmonic from the excitement-fiequency does not constitute the measuringresult, rather such phase-corrected upper wave is produced in each ofthe two channels and these two harmonics are compared with each otherconcerning the phase position.

The comparison of the phase positions and of the amplitudes of theharmonic from the impulse series and corresponding harmonic from theexcitement-frequency takes place suitably such, that the period durationof the harmonic from the excitement-frequency is divided into foursuccessive time sections, while their first and third feeds the filteredoverlying signal of the harmonic from the excitement-frequency and theharmonic of the impulse series to a first integral member and whiletheir second and fourth is stretched to a second integral member andthat at the output of the one integral member the phase position and theoutput of the other controls the amplitude of the harmonic derived fromthe excitement-frequency. The control of the amplitude makes possiblethereby a complete and exact evening of the phase.

Thereby, the switch feeding the overlying signal to the integral memberscan be provided, the switchings of which is controlled by four logicconnection elements, which in turn form the possible combinations of tworectangular voltages and their inverts, whereby the rectangular voltagesare produced from the harmonic derived from the exciting frequency bymeans of presettable phase displacers and by means of triggers in suchmanner, that they have a scanning ratio of l:l and a relative phaseposition of about 90.

With these and other objects in view which will become apparent in thefollowing detailed description, the present invention will be clearlyunderstood, in connection with the accompanying drawing, in which theonly FIGURE discloses a schematic embodiment by example of the presentinvention, whereby the parts of the device are omitted, which concernthe swinging ele ment, the ray-path and the line marking.

These devices are known per se and require no further explanation. Theseknown devices are in operative connection with the device disclosed inthe drawing, so that the light current varied periodically by themovement of the swinging element is impinged upon the photo-electronicmember 1. Furthermore the excitement voltage for the swinging element isavailable at the conduit 2. The electrical signal emitted from thephoto-electronic element 1 is amplified and arrives by means of a switch3 alternately at the channels 4 and 5. The time sections, during whichthe signal is switched to the channels 4 and 5, respectively, determinein accordance with the timely arrangement a rectangular signal 6, whichis derived directly from the excitement-frequency 2 by triggering bymeans of an impulse former step 7. A settable phase displacement 8serves the purpose, to arrange the switching time points of the switch 3such, that they coincide timely with the return time points of theswinging element. Thus in the conduit 4, as well as in the conduit 5, animpulse series each is created. The impulses coincide timely with thetime points, in which by the movement of the swinging element a screenbrushes over the image of the line marking. The impulse series 4 should,by example, produce all over coverings in case of movement in forwarddirection, the impulse series 5, however, all over coverings during thereturn movement of the swinging element. The two impulse series areformed, in known manner, in accordance with the formation of the linemarkings triangularly shaped. In case of an asymmetric formation of theline marking, for instance, an impulse can assume also the form atriangle having non-equal arms.

The position of the line marking is now determined in such manner, thatthe relative phase position of two harmonic oscillations of equalfrequency is determined, which frequency is contained in the impulseseries 4 and 5. For this purpose, a switch each is provided in each ofthe two channels 4 and 5, of which however for drawing reasons only theswitch 9 for the channel 4 is clearly shown, while the switch 10 for thechannel 5 is formed in the same manner.

The impulse series 4 is additively super-imposed with a signal 12 bymeans of an additional amplifier 11, which signal 12 is produced in thefollowing manner: Form the excitement-frequency 2 for the swingingelement the sixth upper wave is produced by the frequency multiplier 13and 14. This 6th upper wave can be separated by means of a filter 15from upper waves of another order number. At the output 16 is disposedin the chosen example thus exclusively the sixth upper wave of theexcitement-frequency 2. This harmonic of the excitement-frequency 2 isfed to automatically operating setting numbers 17 for the amplitude and18 for the phase position. The setting members 17 and 18 are controlledby the output of an integral member 19 and 20 each. Thus it depends fromthe output of the integral member 19, whether a control of theamplitude, and from the integral member 20, whether a control of thephase of the signal 12 takes place. This control occurs such, that apredetermined phase relation between the harmonic contained in thesignal 4 and the har monic 12 derived from the excitement-frequency 2and after controlled by the setting members 17 and 18.

The determination, that a predetermined amplitude ratio and apredetermined phase position exists, takes place in the followingmanner: The harmonic oscillation 12 is fed through a settable face slide21 and 22, respectively. Thereafter, follow an impulse former step 23and 24, each so that at the outputs 25, 26, 27 and 28, two rectangularimpulse successions with a scanning ratio and a relative phase positionof about caused by the rigid setting of the phase slides 2] and 22, arepresent. By logical combination elements 29, 30, 31 and 32, which can,for instance, be Nand elements, the combinations are formed from thesignals 25, 26 and their inverts. Accordingly at the output of theconnection members 29, 30, 31 and 32 output signals occur in timelysuccession, and in particular such, that at each time point an outputsignal occurs only one of these conduits and the durations are of equallength in pairs for the outputs 29 and 31, and 30 and 32, respectively.A switch 33 is controlled by these outputs, which switch 33 switches thesignal 35 delivered from the summary amplifier 11 and freed by a bandfilter 34 from all harmonics, with the exception of the sixth harmonicafter amplification by means of an amplifier 36 to one of the conduits37, 38, 39 and 40 each. The signal 35 should thereby be switched to theconduit 37 during the time period, in which time period an impulse ispresent in the output of the connection element 29, correspondingly tothe conduits 38, 29, 40, if impulses are present at the output of theconnection members 30, 31, and 32. The harmonic 35 is divided in thismanner into four sections, of which those passing the conduits 37 and 39are disposed in a counterphase, as also the sections passing theconduits 38 and 30. Two sections each disposed in a counterphase to eachother are joined and fed to the already mentioned integral members 19and 20. The latter guide, is disclosed above, a fixed phase relationbetween the harmonic 12 derived from the excitement-frequency 2 and theharmonic, which is contained in the impulse series 4.

The accommodation takes place without influence of any errors of thefilter 34. The harmonic 12 is now applied to the comparison with thecorrespondingly formed harmonic from the switch 10. For this purpose theharmonic 12 is triggered in an impulse former step 41 and fed to a phasecomparison circuit 42. The corresponding signal of the switch islikewise fed to the phase comparison circuit 42. An indicationinstrument 43 indicates, in which relative phase position are arrangedthe two input signals of the phase comparison circuit 42. This phaseposition constitutes a measure for the line position. The indication is,aside from the previously mentioned non-sensitivity, relative to thephase distortions, by the filter 34 and the filter correspondingtherewith in the circuit 10, non-sensitive relative phase distortions bythe filter 15.

While l have disclosed one embodiment of the present invention, it is tobe understood that this embodiment is given by example only and not in alimiting sense.

lclaim:

l. A photo-electric device for the determination of the position of linemarkings adapted to be used with a swinging element in a path throughwhich a light stream impinging upon a photo-electronic element isperiodically varied, comprising a switch adapted to be controlled by themovement of said swinging element,

a photo-electronic element means emitting an electric output signal andadapted to be dependent on the light variation caused by said swingingelement and an image of a line marking in the swinging plane of theswinging element,

two separate channels,

said switch connecting alternately said electric output signal with oneof said channels,

means for causing the connecting alternately of said electric outputsignal with one of said channels to take place at about the back andfourth swinging turning point of said swinging element, so that thereciprocation of said swinging element causes a series of impulses insaid two separate channels,

means for the determination of the relative phase position of twoharmonic oscillations of equal frequency, contained in each of saidseries of said impulses including means for production of harmonicoscillations from an excitement frequency of said swinging element, and

a phase slide means each for said harmonic oscillation for bringingabout said harmonic oscillation produced from the excitement frequencyinto a fixed phase relation relative to harmonic oscillations of equalfrequency contained in both of said series of impulses.

5&3? lgl'fifvi'iiif %2 1l i3liul$lll#l laid harmonies from theexcitement frequency into four successive time section for thecomparison of the phase positions and of the amplitudes of the harmonicfrom the series of impulses and the corresponding harmonics from theexcitement frequency.

means for superimposing and filtering a signal of the harmonics from theexcitement frequency and the harmonics of the series of impulses,

a first integrating member connected to receive the filtered superposedsignal of the harmonics from the excitement frequency and the harmonicsof the series of impulses fed by a first and a third of said timesections,

a second integrating member connected to receive said filteredsuperposed signal fed by a second and a fourth of said time sections,and

a first operating setting means controlled by the output of said firstintegrating member for controlling the phase of the harmonics from theexcitement frequency, and

a second operating setting means controlled by the output of said secondintegrating member and for controlling the amplitude of the harmonicderived from the excitement frequency.

3. The device, as set forth in claim 2, which includes a second switchconnected to and feeding said filtered superposed signal to saidintegrating members,

four logic connection means for controlling the switching of said secondswitch,

two impulse former triggers connected to the output of said phaseslides, respectively, and for each producing one rectangular voltagesignal and invert thereof from said harmonics derived from theexcitement frequency such that they have a scanning ratio of 1:1 and arelative phase position of about and conduit means for feeding all thepossible different combinations of said rectangular voltage and invertsthereof, one from each of said impulse former triggers to each of saidfour logic connection means for controlling the latter.

4. The device, as set forth in claim 2, including a phase comparisonmeans for comparing said harmonic from one channel which is controlledin relation to its phase position by the excitement frequency with thecorresponding controlled harmonic from the other channel for theformation of a measuring value for the position of the line markings.

* I I Q

1. A photo-electric device for the determination of the position of linemarkings adapted to be used with a swinging element in a path throughwhich a light stream impinging upon a photoelectronic element isperiodically varied, comprising a switch adapted to be controlled by themovement of said swinging element, a photo-electronic element meansemitting an electric output signal and adapted to be dependent on thelight variation caused by said swinging element and an image of a linemarking in the swinging plane of the swinging element, two separatechannels, said switch connecting alternately said electric output signalwith one of said channels, means for causing the connecting alternatelyof said electric output signal with one of said channels to take placeat about the back and fourth swinging turning point of said swingingelement, so that the reciprocation of said swinging element causes aseries of impulses in said two separate channels, means for thedetermination of the relative phase position of two harmonicoscillations of equal frequency, contained in each of said series ofsaid impulses including means for production of harmonic oscillationsfrom an excitement frequency of said swinging element, and a phase slidemeans each for said harmonic oscillation for bringing about saidharmonic oscillation produced from the excitement frequency into a fixedphase relation relative to harmonic oscillations of equal frequencycontained in both of said series of impulses.
 2. The device as set forthin claim 1 including means for dividing the period duration of saidharmonics from the excitement frequency into four successive timesection for the comparison of the phase positions and of the amplitudesof the harmonic from the series of impulses and the correspondingharmonics from the excitement frequency, means for superimposing andfiltering a signal of the harmonics from the excitement frequency andthe harmonics of the series of impulses, a first integrating memberconnected to receive the filtered superposed signal of the harmonicsfrom the excitement frequency and the harmonics of the series ofimpulses fed by a first and a third of said time sections, a secondintegrating member connected to receive said filtered superposed signalfed by a second and a fourth of said time sections, and a firstoperating setting means controlled by the output of said firstintegrating member for controlling the phase of the harmonics from theexcitement frequency, and a second operating setting means controlled bythe output of said second integrating member and for controlling theamplitude of the harmonic derived from the excitement frequency.
 3. Thedevice, as set forth in claim 2, which includes a second switchconnected to and feeding said filtered superposed signal to saidintegrating members, four logic connection means for controlling theswitching of said second switch, two impulse former triggers connectedto the output of said phase slides, respectively, and for each producingone rectangular voltage signal and invert thereof from said harmonicsderived from the excitement frequency such that they have a scanningratio of 1:1 and a relative phase position of about 90* and conduitmeans for feeding all the possible different combinations of saidrectangular voltage and inverts thereof, one from each of said impulseformer triggers to each of said four logic connection means forcontrolling the latter.
 4. The device, as set forth in claim 2,including a phase comparison means for comparing said harmonic from onechannel which is controlled in relation to its phase position by theexcitement frequency with the corresponding controlled harmonic from theother channel for the formation of a measuring value for the position ofthe line markings.